Transcript
UPGRADING THE ELECRAFT K2 TO RE VISION B Rev. D, Jan 4, 2003
In October, 2002, the K2 transceiver was updated to incorporate many modifications that had been recommended by Elecraft or our customers. Any Revision A K2 (or Revision XC, 1999 Field Test) can be brought up to Revision B by making the changes listed in Table 1. K2s with serial numbers 3000 and higher already include all of the changes. To determine which revision of the K2 you have, look at the RF board, near "ELECRAFT" label at the center. All of the modifications can be made inconspicuously: added parts are soldered to the side of each board that is least visible when the cover is removed. This will preserve the appearance of your transceiver. Most of the items needed are supplied with the K2ATOBKT mod kit. Other mod kits and parts must be purchased separately as indicated in the table; these kits come with their own modification instructions. Step 9 (AF GAIN control modification) does not require a mod kit, but you'll still need to obtain the associated application note (see page 8). If your present K2 firmware is older than revision 2.00A, you'll need a firmware upgrade (part # FWK2MCIO) in addition to any hardware mod kits. New firmware installation and realignment will be done in steps 11 and 12, after all desired hardware changes have been made. This ensures that calibration and test steps will only have to be performed once.
Table 1. Modification Steps Board(s)
Part #
Pg.
1. Firmware Revision Check and Parameter Save
RF
n/a
3
2. PLL Frequency Stability at 7182 kHz
RF
K2ATOBKT
5
3. Misc. RF Board Changes
RF
K2ATOBKT
6
4. 15/17 meter and 20/30 meter Band-pass Filters
RF
K2ATOBKT
7
5. PLL and BFO Temperature Stability
RF
BFOMDKT
7
6. VFO ALC and 10/12 meter Band-pass Filter
RF
E850093
7
7. Second Crystal Filter Flatness
RF
XFILMDKT
8
8. First Crystal Filter Grounding
RF
n/a
8
9. AF GAIN Control Smoothness
All three
n/a
8
10. Misc. Control Board Changes
Control
K2ATOBKT
9
11. Firmware Installation
Control, RF
FWK2MCIO
10
12. Alignment and Test
Control, RF
n/a
10
13. Speaker Grille Cloth
n/a
E850089
15
Modification Steps (do in order)
NOTE: Not included are Rev. B board changes that accommodate the K60XV 60 meter adapter (RF board: VCO and 40-m low-pass filter). The K60XV manual describes these changes, which should not be made until the option is installed. Also not included are minor changes that have no impact on operation or performance (for example, RF board: R60 bias pot changed to a fixed 100-ohm resistor; Control board: switch S1 changed to a jumper block, P7).
1
K2ATOBKT Mod Kit Inventory The parts supplied with K2ATOBKT mod kit are listed below. Other mod kits referenced in Table 1 include their own parts lists.
Ref. RF-C33 RF-C68 RF-C28,C29 RF-CPLL RF-C174 RF-C30,C36 RF-C91 CTRL-C12 RF-CRF, CTRL-C31 CTRL-C42 RF-D10 RF-R50 RF-R64,CTRL-R6 RF-R1, R2 CTRL-R12 CTRL-R7 RF-RREFA, RREFB RF-R11 RF-R18 RF-RFC11 RF-RFC15 CTRL-L1 Misc.
Description Capacitor, 2 pF ("2") or 2.2 pF ("2r2") Capacitor, 10 pF Capacitor, 12 pF Capacitor, 68 pF Capacitor, 82 pF Capacitor, 470 pF ("471") Capacitor, .001 µF ("102") Capacitor, .0027 µF ("272") Capacitor, .047 µF ("473") Capacitor, 0.1 µF ("104") Diode, ultra low-drop Shottky, 95SQ015 Resistor, 1.5 ohms, 1/2 watt (brown-green-gold) Resistor, 100 ohms, 1/4 watt (brown-black-brown) Resistor, 220 ohms, 1/4 watt (red-red-brown) Resistor, 820 ohms, 1/4 watt (gray-red-brown) Resistor, 1.78 k, 1/4 watt, 1% (brown-violet-gray-brown) Resistor, 10 k, 1/4 watt (brown-black-orange) Resistor, 47 k, 1/4 watt (yellow-violet-orange) Resistor, 1 M, 1/4 watt (brown-black-green) Toroid, 20 turns #26 enamel on FT37-43 core RF choke, miniature, 100 µH (brown-black-brown) Inductor, shielded, 82 mH ("823", dark gray, cylindrical) Enamel wire, #26, red (for RFC11)
Part
Qty
E530047 E530006 E530058 E530007 E530038 E530004 E530001 E530055 E530025 E530011 E560009 E500025 E500010 E500002 E500001 E500026 E500015 E500067 E500024 E680003 E690013 E690015 E760002
1 1 2 1 1 2 1 1 2 1 1 1 2 2 1 1 2 1 1 1 1 1 3 ft.
i
Caution: Some parts in the K2 can be damaged by static discharge. While making modifications, use an anti-static wrist strap. Alternatively, you can touch a grounded, unpainted metal surface (do this often).
i
Updating the K2 to revision B involves a considerable amount of component removal. You will need a full-size, hand-operated vacuum desoldering tool. The Edsyn model AS196 Anti-Static Solder Sucker ($25), is an excellent choice. Before removing a component, straighten its leads on the solder side (use a small tool while heating the solder joint). Next, clean out the holes using the desoldering tool. Finally, pull the component out, being very careful not to damage pads, plated-through holes, or traces on the top or bottom sides of the board.
2
Supplemental Menu Parameters: The D I S P L A Y switch is used to access additional parameters when editing certain menu entries. These include sidetone source (S T L entry), 8R Hold mode (T - R entry), Auto-Detect mode (I N P entry), and Fan mode (P A entry, secondary menu). These will be set up appropriately during new firmware installation (page 10) and do not need to be recorded here.
1. Firmware Check and Parameter Save Determine what revision of firmware you have by turning the K2 on while pressing and holding any switch. You'll see a display such as: 2 . 0 3 d 1 . 0 7 . The number on the left is the firmware revision of the main microcontroller, U6 on the Control board. The other number is the firmware revision for the I/O controller (IOC), U1 on the RF board. Record both of the numbers here: K2 _______ IOC _______.
CAL Settings (Table 3): To access CAL settings, use the primary menu to scroll to C A L , hold E D I T to edit the parameter, select a CAL function with the VFO knob, then hold E D I T again to activate the function. After recording the setting, tap M E N U to exit, then tap M E N U again and access the next CAL function in the same manner.
i
If your K2 firmware revision is older than 2 . 0 0 A , you'll need to install new firmware after making all desired hardware changes. You may need to install a new IOC in addition to the main microcontroller. This will be explained later. Whether or not you plan to install new firmware, you should record your present configuration settings in Tables 2 - 5. The BFO frequencies (Table 5) will be needed if you make the Temperature Stability changes.
Table 3. C A L Settings CAL Function OFF FCTR CUR TPA S LO S HI PLL FIL
Table 2. Menu Parameters Primary Menu Entry ST L ST P T-R RPT INP IAB SSBA SSBC2 LCD GRPH OPT ATU RANT CAL PF1 PF2
Param.
SSBC
SSBCr
Table 3
Secondary Menu (Rev. 2.00 up1) Entry Param. SLCH RATES DOT FPLY PORT SPLT Po28 RTTY RTC RIT ACC AT2/D193 PA TRN1 Table 4 TRN2 TRN3
Parameter n/a n/a n/a (stored by KPA100)
n/a (CAL PLL will be done later) Table 5
Transverter Band Displays (Table 4): You'll only need to record these settings if you use the transverter bands. To access transverter band display settings, tap M E N U , then tap D I S P L A Y to switch to the secondary menu, then scroll to the desired T R N x menu entry. Hold E D I T to access it. Tap D I S P L A Y to cycle through the five parameters for each transverter band display. To select the next transverter band setup, first tap M E N U to return to scroll mode. Table 4. T R N x Band Displays (Rev 2.00 up) Xvtr #
On /Off
RF
IF
OFS
TRN1 TRN2 TRN3
1
To switch between the P R I and S E C menus, tap D I S P L A Y after tapping M E N U . 2 If RTTY is set to O N (Rev 2.00 up), and r mode has been selected with M O D E , the S S B C menu entry changes to S S B C r . Record both settings if applicable.
(see next page for Table 5)
3
If you have revision 2.03 or later firmware, the name of this menu entry is D 1 9 . Otherwise it is A T 2 (which was never used).
3
OUT
Filter and BFO Settings (C A L F I L , Table 5)4: Before recording filter/BFO data, switch to 17 meters or lower (so LSB/USB settings won't be swapped in CAL FIL). Connect the internal frequency counter cable to TP2 (BFO). To access filter and BFO settings, tap M E N U , scroll to C A L , hold E D I T to access the parameter, and change it to F I L . Hold E D I T again to activate the C A L F I L function. Record filter bandwidth settings (e.g. 0 . 7 0 ) for each mode and each filter. Cycle through the modes by tapping M O D E and holding C W R E V when appropriate; filters are selected using X F I L . (RTTY mode, r , and RTTY reverse are only available with revision 2.00 and up firmware. The associated secondary menu entry, R T T Y , must be set to O N .) After all filter bandwidths are recorded, tap B A N D followed by D I S P L A Y to show the BFO frequency. Record the BFO frequencies (e.g., 4 9 1 3 . 1 0 ) for each mode and filter, as you did for the filter bandwidths.
Table 5. Present Filter and BFO Settings (C A L F I L ) Mode
FL1
BF1 t
FL2
BF2
FL3
BF3
FL4
BF4
CW CW Rev. LSB USB RTTY RTTY Rev.
4
If you're not familiar with filter and BFO configuration, review the instructions for CAL FIL in the K2 Owner's manual, starting on page 85.
4
2. PLL Frequency Stability at 7182 kHz Whenever the VFO is tuned to the 5 kHz band segment centered at about 7182 kHz, the PLL reference oscillator and VCO will be at exactly the same frequency. At this point, on a small percentage of K2s, coupling between the two oscillators can result in a "wavering" quality on both transmit and receive. If your K2 exhibits this symptom, it must be corrected. It compromises signal quality, and may prevent VFO linearization (CAL PLL) from working correctly.
Pin 13
Frequency Stability Test MC145170 (bottom view)
You'll first need to identify the segment of 40 meters over which the two oscillators are at the same frequency. Switch to 40 meters, LSB or CW mode, and tune to about 7182 kHz. Then activate C A L F C T R using the menu. Alternately insert the internal counter probe into TP1 (VCO) and TP3 (PLL reference oscillator), and make sure they indicate the same frequency (in the 12 MHz range). They'll be equal over some 5 kHz segment, typically 7179-7184, but possibly lower or higher5. (Note that you can tune the VFO while in C A L F C T R .) Don't change modes or filters, as this will move the target range.
C90
Figure 1
Pin 16
X
Range: 7____- 7____ kHz (mode: ___, filter: ___ ) Listen to a few signals in this range to see if they exhibit the "wavering" sound. Compare them to signals outside the range. You can use another ham transmitter as a signal generator. (Don't change modes or filters.)
MC145170 (bottom view)
C90
Figure 2
Modifications to Cure Instability The following modifications can be used to cure the instability, if required. Try them in order, and stop when the symptom disappears. All necessary parts are included in mod kit K2ATOBKT.
RFC15
Make sure C70 and C71 (VCO area) have the shortest possible leads. Solder a 68-pF capacitor (RF-CPLL) on the bottom of the RF board, between pins 13 and 12 of the MC145170, U4 (see Figure 1). Keep the lead length short. Add an RF choke in series with U4 pin 16. First locate point "X" in Figure 2. Cut the indicated small trace segment between pin 16 of U4 and capacitor C89 (on the top side). Next, solder a miniature 100-µH RF choke (RFC15) across the cut as shown in Figure 3. Finally, solder a.001-µF capacitor (C91) from pin 16 to ground. Remove C70 (4.7 pF).
C91
C90 Figure 3
5
Due to differences in the way old and new firmware did CAL PLL.
5
3. Misc. RF Board Changes
Add CRF (.047, "473") on the bottom of the RF board as shown in Figure 4. One trace cut is required. (This capacitor is important if you have a KBT2 internal battery or KPA100 module. It prevents damage to the K2's low-pass filter relays in the event that the AUX RF and AUX DC cables are reversed. On the Rev. B RF board, the capacitor is C224.)
This step describes all RF board changes not covered elsewhere. Parts can be found in K2ATOBKT. Turn the K2 off. Touch an unpainted, grounded metal surface. Remove the top cover. Remove all options plugged into the RF board. Remove the two screws holding the Control board to the Front Panel board. Unplug the KAF2 if present. Remove the Front Panel assembly (there is no need to separate the panel from the PC board).
J3
J4
Remove the bottom cover. Remove the rear panel/heatsink. Save all of the PA hardware, including the thermal pads.
Revision XC and older Rev. C K2s Only
Crf K9
The following steps apply to Rev. XC and some Rev. A K2s (prior to s/n 2000). Check the components to see if you already have the correct values installed.
P6
Change C68 (VCO area) from 4.7 or 5 pF to 10 pF. (Eliminates possible VCO problem on 160 meters.)
Cut K10
Change R1 and R2 (near the key jack) from 470 ohms (or 1k) to 220 ohms. (Lowers the voltage seen by the K2 when a paddle is closed. With 1 k, noise immunity may be inadequate. The microcontroller's internal pull-up resistors can pull these lines up too close to the "0" logic threshold.)
Figure 4
Change D10, at the right edge of the RF board, from an SB530 to a 95SQ015. (The latter is an ultralow-drop diode, having a drop of only about 0.1 to 0.2 volts. This reduces wasted power in the diode on transmit, nearly eliminates the discrepancy between external voltmeters and the K2's internal voltage display, and allows the use of a slightly lower voltage supply for recharging the KBT2 internal battery.)
Change R50 from 1/4 watt to 1/2 watt (1.5 ohms, brown-green-gold). (1/4 watt in the driver emitter was too low to ensure adequate heat dissipation.) Note: Other minor (preventative) design changes were made from revision XC to revision A. Except in rare cases, they will not significantly affect performance, and we recommend that they not be changed. These include: L31 from 12 to 10 µH (PLL reference), C153 from 39 to 68 pF (TX mixer coupling), C162 from .01 to .047 (post-mixer amp), D9 from 1N34A to 1N5711 and R68 from 237 to 226 (RF detector).
Re-installing the Heat Sink Note: Skip these two steps for now if you plan to make the bandpass filter changes on the next page. Inspect the thermal pads for Q7 and Q8. Brush away any aluminum fragments which might have become stuck to the pads.
Revision A and XC K2 Change R64 (center of the board, near U1) from 470 to 100 ohms. (Improves auxBus noise immunity.)
Re-install the rear panel/heat sink and PA hardware as described in the K2 owner's manual (Assembly, Part III).
Change RFC11 from an RF choke to an FT37-43 toroid with 20 turns #26 enamel. Mount RFC11 on the bottom of the board with short leads. (Reduces unwanted S-meter activation, esp. on 17 meters.) 6
4. 15/17 m & 20/30 m Bandpass Filters
If you have an older K2 (Rev. A or XC), you may have installed a large capacitor (150 pF or larger) at C174 due to inadequate BFO range. Increasing only the size of C174, without a proportional increase in C173, may cause excessive BFO injection and is no longer recommended. Restore C174 to its original value if applicable (82 pF; supplied with K2ATOBKT.)
See descriptions below. Band-pass filter realignment will be done following all hardware and firmware updates.
15/17 m Bandpass Filter These optional changes narrow the 15/17 m bandpass filter to improve image rejection. In Europe in particular, strong shortwave broadcast stations in the 16 MHz range may produce low-level image responses in the 15-m band with the original filter values.
Note: The crystals supplied with BFOMDKT should have adequate range with the standard capacitor value at C174 (82 pF). If the range is found to be slightly low, two supplemental capacitors (47 pF and 120 pF), which are supplied with BFOMDKT, can safely be added in parallel with C174 and C173. This is explained on page 12 as part of the BFO range test.
Change C30 and C36 from 330 to 470 pF ("471"). Change C33 from 3 (or 3.3) pF to 2 (or 2.2) pF.
20/30 m Bandpass Filter
If you have an older K2 (Rev. A or XC), you may have a 100 k RPACK at RP2. In this case, solder 10 k resistors (RREFA, RREFB) across RP2 pins 1-2 and pins 3-4, on the bottom of the board in the VCO area. (There's no need to remove RP2, which can be difficult. The two paralleled resistors will suffice.)
This optional change adds 12-pF capacitors in parallel with each of the 20/30-m bandpass filter trim caps, which should eliminate any difficulty in aligning the bandpass filter on 20 meters. Some builders found that the 20-meter trimmers "topped out" before the peak was located.
Locate the instructions supplied with BFOMDKT. Put an "X" by the instructions covering installation of firmware, as well as BFO and PLL test and alignment. These steps will be skipped for now.
Solder 12 pF capacitors across C21 and C23, on the bottom of the board in the bandpass filter area. (These capacitors are designated C28 and C29 on the Rev. B RF board.)
Follow all instructions supplied with part # BFOMDKT, except those you marked with an "X" above.
Re-installing the Heat Sink Inspect the PA thermal pads and re-install the heat sink as described in the last two steps on page 6.
6. VFO ALC & 10/12 m Bandpass Filter This set of modifications enhances the VFO ALC circuit and narrows the 10/12 m filter. Without the mods, a small increase in VFO spurious output will sometimes occur when switching bands to or from 10 meters. This is usually significant only if the K2 is driving a KPA100 or other amplifier, but we recommend making the changes in all cases. The parts and documentation for this mod are supplied with part # E850093.
5. PLL and BFO Temperature Stability This optional set of modifications reduces BFO frequency drift an average of 70-80%, and VCO drift an average of 30-40%. The parts and documentation for the change are supplied with part # BFOMDKT. If you previously installed this mod kit, make sure that R19 (soldered to the bottom of the board in the PLL reference oscillator area) is 2.7 k. Some early BFOMDKT kits were sent out with 220 ohms for use at R19, which can cause PLL reference oscillator instability. (1.8 to 3.3 k can be used.)
Follow all instructions supplied with the VFO ALC mod kit, E850093, except 10/12 meter bandpass filter alignment. Alignment will be done later.
Note: Skip to step 6, at right (VFO ALC and 10/12 m Bandpass Filter) if you've already installed BFOMDKT.
If you have a rev. XC K2, you must also add R18 (1 M) to the VFO ALC circuit. Solder R18 on the bottom of the board, directly across the pads of C59.
7
7. Second Crystal Filter Flatness
i
In the following step, be careful not to overheat the crystals. Use a temperature-controlled iron, and limit soldering time to about 3 seconds per soldering attempt.
This change flattens the K2's second crystal filter response, and allows the I.F. adjustment, L34, to be set optimally for both CW and SSB. As a result, a much better pitch match can be obtained on LSB and USB. The parts and documentation for this mod are supplied with part # XFILMDKT. Follow all instructions supplied with XFILMDKT, except those instructions dealing with I.F. alignment, which will be done later.
There are two ground pads each for X7-X11, one on either side. Use bare wires (10 total) for grounding the crystals, but do not solder the wires to the tops of the crystals. The wires must be soldered to the sides, instead, about 1/4" (6 mm) up from the surface of the PC board.
8. First Crystal Filter Grounding
9. AF GAIN Control Smoothness
The instructions for grounding the crystals in the 5pole first CW crystal filter (X7-X11) originally called for the wires to be soldered to the tops of the cans. A few builders subsequently determined that soldering the ground wires closer to the base of the cans resulted in better ultimate attenuation. Some builders also experimented with additional bypassing of filter control lines using surface-mount capacitors, but this appears to offer very little additional benefit, if any.
The original "2-wire" AF gain potentiometer circuit is susceptible to mechanical potentiometer noise at the counter-clockwise end of its rotation. The "3-wire" modification used in the Rev. B K2 completely eliminates this problem, making AF GAIN adjustment smooth. The modification also allows the AF GAIN pot to completely turn off the audio when rotated fully counter-clockwise. In some cases, the old circuit would permit some residual signal to circumvent the potentiometer in this position.
This change is optional. Most K2 builders who used top-grounding of the crystals in the first crystal filter found the ultimate attenuation to be completely satisfactory.
This change is optional but recommended. Follow all instructions in the application note, except those dealing with testing the new circuit, which will be done later. The application note can be found at: http://www.elecraft.com/Apps/K2_AF_pot/K2_AF_gai n_app_note.htm (HTML) or: http://www.elecraft.com/Apps/K2_AF_pot/K2_AF_gai n_app_note.pdf (PDF)
8
10. Misc. Control Board Changes
Sidetone Modification
These changes improve various operating characteristics of the K2, as explained in each of the steps below. The parts for these changes are included in K2ATOBKT.
These optional changes provide a more pleasantsounding sidetone. Locate capacitor C24 (.0027 µF), which is on the right side of the Control board between RP7 and RP3. As shown in Figure 6, cut the trace on the top side of the board between C24 and pin 6 of RP7. On the bottom side of the board, solder a 47 k resistor (yellowviolet-orange) between these two pads. (Reduces digital switching noise in the sidetone; designated R11 on the Rev. B Control board.)
Change R6 from 470 to 100 ohms (brown-blackbrown). (Improves auxBus noise immunity.) Change R7 from 1.96 to 1.78k (brown-violetgray-brown). (Improves current measurement accuracy.) Change C12 from .001 to .0027 µF ("272"). (Improves auxBus noise immunity.)
R11 (on back)
Change C42 from .01 to 0.1 µF ("104"). (Stabilizes voltage display.)
RP7
Locate the trace on the top side of the board that runs directly between resistors R8 and R9 (Figure 5). Cut the trace. On the bottom side of the board, solder an 820-ohm resistor (gray-red-brown) between the two vias. You'll need to pre-trim the resistor's leads since it isn't possible to cut the lead that falls between R8 and R9. (Protects the microcontroller in the event that an RS232 signal is accidentally connected to the VRFDET line via the KIO2's or KPA100's AUX I/O connector. Designated R12 on the Rev. B Control board.)
Cut
R8 R9
RP7
C24
C24
Cut Figure 6
Locate RP5, the 10-pin, 470-ohm RPACK at the right side of the board. Solder an 82-mH shielded inductor ("823") on the bottom of the Control board between pins 7 and 10 of RP5. The leads of the inductor should be formed such that the body can be folded down flat against the PC board. (Designated L1 on the Rev. B board. Creates a low-frequency resonant tank in conjunction with C33, greatly attenuating harmonics of the sidetone. The resonant frequency is approximately 400 Hz, but the Q is quite low, so sidetone frequencies from 400-800 can still be used effectively.)
R12 (on back) RS-232 and Sidetone Source (KIO2/KPA100) If either a KIO2 or KPA100 option is installed in the Rev. A or XC K2, the builder must make a few additional changes to the Control board. These changes are fully documented in the KIO2 and KPA100 manuals. (The sidetone generation is re-routed from pin 25 of the microcontroller, U6, to pin 4 of the quad D-to-A converter, U8. This allows pin 25 of U6 to be used for full-duplex RS232 communications.)
Figure 5
If you have an older K2 (Rev XC or A), C31 may be 0.1 µF ("104"). Change C31 to .047 µF ("473"). (Improves CW keying envelope shape.)
There is no need to make these changes until you add a KIO2 or KPA100. In a later step, you'll set up your K2's configuration based on whether or not you have at some point installed either of these options.
9
AGC Threshold Control
12. Alignment and Test
R1 on the Control board sets the AGC threshold, which also establishes the K2's I.F. gain. On Rev. A and Rev. XC Control boards, R1 is fixed. A small number of K2 owners found that reducing the size of R1 slightly could optimize the AGC threshold setting and/or bring up the I.F. gain, so we used a trimmer at R1 on the Rev. B board.
Re-Installation of Boards and Panels Reinstall the front panel assembly. Reinstall the Control board (and KAF2 option if applicable). Secure the Control board to the Front Panel board using the provided hardware. Reinstall the bottom cover.
We don't recommend replacing R1 with a trimmer on older K2s, for two reasons: the number of K2s that would benefit from it is quite small; and adding a potentiometer here is difficult because R1 is very close to the side panel.
Reinstall all options that plug into the RF board. Reinstall the rear panel/heatsink if you have not done so already (last two steps on page 7).
After you've completed all hardware changes and have the K2 reassembled, you can test your AGC threshold to determine if a change in the value of R1 is warranted. This is covered in on page 14.
Firmware Configuration Turn on the K2. You may see I N F O 2 0 1 (for about 11 seconds) if you have installed new firmware. The sidetone may not be working at this point, and the filters and S-meter may not be calibrated.
11. Firmware Installation
If you saw I N F O 2 0 1 , you must re-enter all of your menu and CAL parameters as explained in the following steps. If you didn't see INFO 201, skip to Supplemental Menu Parameters (next page).
If you determined earlier (page 3) that your firmware must be replaced, complete the following steps. Otherwise skip to Alignment and Test (right column).
Set up all primary menu entries using data recorded in Table 2 (page 3). S T L and S T P must be set up, even though you may not have any sidetone at this point. This will be corrected later.
Touch an unpainted, grounded metal surface. Remove the old K2 firmware, U6 (Control board), using a small screwdriver to pry it gently out of its socket at both ends. Store it in a safe place.
If your old firmware was older than revision 2.00, please read the "K2 Revision 2 Firmware" manual, which you should have received with the new firmware (you can also download it from our web site). This will explain what the secondary menu entries are used for, and how to access this menu.
Straighten the leads of the new microcontroller (PIC18C452). Install the new microcontroller. Orient the notched or dimpled end of the IC with the notched end of its component outline.
Set up all secondary menu entries from Table 2. If your I/O controller (IOC) firmware is revision is 1.05 or earlier, or if you were sent a new I/O controller by Elecraft (PIC16F872), remove U1 on the RF board. Store it in a safe place. Install the replacement IOC at U1.
If you have the K60XV option installed (60 meter adapter), set the D 1 9 secondary menu entry to Y (see K60XV manual). Set up the C A L C U R , C A L S L O , and C A L S H I entries from Table 3. C A L T P A is stored by the microcontroller in the KPA100, if applicable, and does not need to be set up here. C A L P L L will be done later. If applicable, set up transverter bands (Table 4). Set up the filter bandwidths (but not the BFOs) for each mode using data from Table 5. The BFOs will be set up after the BFO range check. 10
Supplemental Menu Parameters
PLL Reference Oscillator Range Test
The D I S P L A Y switch is used to access additional parameters when editing certain menu entries. Set up these parameters as follows:
This test is necessary if you made the Temperature Stability modifications or changed any other components in the PLL reference oscillator.
Test your sidetone using the S T L menu entry. If the sidetone is missing, E D I T the S T L parameter, then tap D I S P L A Y to change the sidetone source. The default is U 8 - 4 , compatible with the Control board modifications required for the KPA100 and KIO2. If you have never installed a KIO2 or KPA100, the source should be set to U 6 - 2 5 .
Make sure the bottom cover is securely attached, and that the K2 has been turned on for at least 5 minutes (operating at room temperature). Plug the frequency counter probe into P6 (Control board). Connect the probe tip to the PLL reference oscillator test point, TP3 (left-front corner of the RF board, near U4). Note: If a KAF2 module is installed, you'll need to temporarily remove it to get to TP3.
"8R Hold" mode keeps the 8R (8 volts receive) line low between CW elements. This is now the default mode for 8R; it eliminates excessive T-R relay switching when the K2 is used with transverters or amplifiers. At present we don't know of any reason to set the 8R mode to "normal," where 8R is allowed to go back to 8 volts between CW elements. However, if you wish to select this mode, locate the T - R menu entry, E D I T its parameter, and tap D I S P L A Y . You'll see 8 R n o r on the LCD.
Using the menu, select C A L F C T R , then hold E D I T a second time to enable the frequency counter. The counter should show a frequency of 1 2 0 9 0 kHz +/- 30 kHz. If it is 0000.00, changing rapidly, or out of range, you could have a problem with the counter probe or the PLL Reference Oscillator.
"Auto-detect" allows you to connect a keyer, computer, or hand key to the K2 along with a keyer paddle. Auto-detect is normally on. To turn it off, locate the I N P menu entry, E D I T its parameter, and tap D I S P L A Y . You'll see A D E T O F F .
When you’re in frequency counter mode, the B A N D + and B A N D - switches can be used to check the range of the PLL reference oscillator. First, tap B A N D + and write down the frequency reading in the space below (typically about 12097-12100 kHz). Then tap B A N D - and write down this frequency reading (typically 12085-12090 kHz).
The default fan mode for the KPA100 option is F A N n o r . If you prefer F A N L o H i or F A N H i , locate the P A entry in the secondary menu, E D I T the parameter, and tap D I S P L A Y to select the desired mode.
Ref. High Freq. Ref. Low Freq. Range (kHz) ____________ ____________ __________ Subtract the lower frequency reading from the higher reading. The range must be between 9.3 and 13 kHz (if not, you may have a problem in the PLL reference oscillator, most likely with one of the components recently installed). Tap M E N U to exit C A L FC T R . If you removed the KAF2 option temporarily to get to test point TP3, reinstall it now.
11
BFO Test
If your BFO range is slightly less than 3.6 kHz, and/or the low frequency is higher than 4912.7, your BFO crystals probably have higher than average Q. You can safely compensate for this by increasing the size of C174 and C173 in the BFO circuit. The Temperature Stability mod kit (BFOMDKT) includes two capacitors for this purpose, 47 pF to parallel with C174, and 120 pF to parallel with C173. If you didn't order this mod kit, you can use any temperature-stable capacitors (NPO, C0G, or N750 types) in the following ranges: 39-68 pF (in parallel with C174), and 100-180 pF (in parallel with C173).
The BFO will be tested in the following steps. You should do this test even if you did not make the Temperature Stability modifications. Make sure the bottom cover is securely attached. Switch to the 40-m band. Connect the frequency counter to the BFO test point (TP2), which is on the right side of the RF board near the crystal filter. Using the menu, activate C A L F C T R . The counter should show a frequency between 4908 and 4918 kHz.
If the BFO doesn't appear to be working, or its frequency range is shifted too high or too low, it may be due to one of the following:
i
If you see a reading of 0 0 0 0 . 0 0 kHz or one that is changing rapidly, you may not have the frequency counter probe connected properly. Also inspect the leads of L33 carefully. They could be broken or poorly soldered.
When you’re in frequency counter mode, the B A N D + and B A N D - switches can be used to check the range of the BFO. First, tap B A N D + and write down the frequency reading below (typically about 4916-4917 kHz). Then tap B A N D - and write down this frequency reading (usually about 4911-4913 kHz). Finally, calculate the BFO range (high - low) in kHz. Typical range is 4 to 5 kHz.
If you didn't calibrate the K2's internal frequency counter using an external counter, it may not be reading accurately. If possible, borrow an accurate counter and re-do the 4 MHz Oscillator Calibration as described in the K2 owner's manual. If you installed the new BFO toroid at L33 (T44-7), look closely at its leads using a magnifying glass. The wire used is very small, and easily broken during installation. One or more of the capacitors in the BFO circuit could be of the wrong value.
BFO Alignment The following two steps will be necessary if you saw I N F O 2 0 1 on the display following firmware installation, or if you made the Temperature Stability modifications to the BFO.
BFO High Freq. ___________ (must be 4916.3 kHz or higher)
Make sure the bottom cover is securely attached.
BFO Low Freq. ___________ (must be 4912.7 kHz or lower)
Set up the BFOs for all modes and filters using the frequencies from Table 5 (page 4). You'll have a chance later on to fine-tune the BFO settings.
Range (High - Low) ___________ (must be 3.6 kHz or more)
12
VFO Linearization
I.F. Amplifier Alignment
This procedure will be necessary if you installed new firmware or if you made the Temperature Stability modifications to the PLL reference oscillator. The procedure will be done only on 40 meters. It should not be repeated on each band.
If you made the recommended modification to the second crystal filter, L34 will need readjustment. L34, located near the right front corner of the RF board, is used to peak the output of the I.F. amplifier. Using the wide end of the plastic tuning tool, adjust the slug in L34 until it is near the top of the can. Stop turning the slug when it appears to be at the top or when you feel resistance.
Allow the K2 to warm up at normal operating room temperature for at least five minutes. The bottom cover must be installed. Plug the K2 frequency counter cable into P6 on the Control board. Connect the probe end to test point TP1 on the RF board (VCO, center-left side of the RF board).
Turn L34’s slug one full turn clockwise (down into the can). Set the band to 40 meters using B A N D + or B A N D - . Select CW Normal and FL2 (700 Hz nominal bandwidth).
Switch to 40 meters and set the VFO to about 7100 kHz.
Make sure the RF GAIN control is fully clockwise (max. gain). Disconnect the antenna from J4, if one was connected.
Tap M E N U and locate the C A L entry. Hold E D I T , then change the parameter to P L L . Hold E D I T again to begin the calibration procedure. You'll see a frequency in the 12 MHz range displayed, and the letter "d " will flash as the firmware records calibration data. After approximately 5-10 minutes, you'll hear a short tone, and E N D will be displayed. Tap any switch to clear this message.
Tap P R E / A T T N until the PRE annunciator turns on. Connect a pair of headphones (stereo or mono) to the front panel jack, and turn the AF GAIN control to about midway. Slowly tune the VFO to locate the weak internally-generated signal near 7000 kHz.
i
If you see I N F O 2 3 2 at any time during VFO calibration, verify that you were on 40 m, with the counter cable at TP1.
While listening to the signal at 7000 kHz, adjust L34 for best signal strength and lowest noise. This setting occurs at about 1 to 1.5 turns below the top of the can. (You can use your DMM on AC volts, at the speaker jack, to obtain a more sensitive indication.)
You can check the VFO's accuracy using a signal at a known frequency (see page 98 of the revision C K2 manual). Note: In the Revision C manual, steps 8 and 11 on page 98 are incorrect for the new firmware. C A L P L L is now run only once, and only on 40 m. Move the K2 counter cable to the BFO test point, TP2.
13
Receiver Pre-Alignment, 10-30 meters
Transmitter Alignment, 10-30 Meters
This step is necessary if you made any changes to the 10-30 m band-pass filters (steps 4, and 6, page 7). If you didn't make these changes, continue with FineTuning Filter Settings, page 15.
Set the POWER control for 2.0 watts. Connect a dummy load at the antenna jack. Switch to 30 meters. Adjust L8 and L9 for maximum power output in TUNE mode. Avoiding using TUNE mode for more than 5 seconds at a time.
Switch to 20 meters and set the VFO for about 14100 kHz.
Switch to 20 meters (14100 kHz) and adjust C21 and C23 for maximum power output.
Turn on the RF preamp by tapping P R E / A T T N until you see the PRE annunciator turn on.
Switch to 15 meters (21100 kHz) and adjust L10 and L11 for maximum power output.
Use a signal generator or an antenna to inject a signal or noise at this frequency.
Switch to 17 meters (18100 kHz) and adjust C32 and C34 for maximum power output.
i
Since some inductors are shared between two bands, you must always align the bands in the order indicated. Always use this procedure if you re-align the filters later.
Switch to 10 meters (28200 kHz) and adjust L12 and L13 for maximum power output. Switch to 12 meters (24900 kHz) and adjust C44 and C46 for maximum power output.
Set C21 and C23 to their mid-points. Adjust L8 and L9 for maximum signal strength. (This step presets C21, C23, L8, and L9 before final adjustment in the next two steps.)
AGC Threshold Test A few K2 builders found that their overall receive gain was too low because of a less-than-ideal AGC threshold setting. If you think you might benefit from a change in this threshold, follow the steps below. Otherwise, skip to the next page.
Note: When switching to each of the remaining bands to be aligned, you'll need to inject a signal or use an antenna. Switch to 30 meters (10100 kHz) and turn on the preamp. Adjust L8 and L9 for maximum signal strength.
Connect an antenna to the K2, and switch to a quiet band (one with little atmospheric noise). Turn AGC off by holding the P R E / A T T N and A G C switches together.
Switch back to 20 meters (14100 kHz). Adjust C21 and C23 for maximum signal strength.
If the level of background noise increases significantly with AGC off, even on a quiet band, you may benefit from an adjustment to the AGC threshold. Remove the Control board and temporarily substitute a potentiometer for R1, presetting it to R1's fixed value. Once you find a value of R1 that brings I.F. gain up slightly while not compromising AGC performance on large signals, you can install a fixed resistor of that value.
Switch to 15 meters (21100 kHz) and turn on the preamp. Adjust L10 and L11 for maximum signal strength. Switch to 17 meters (18100 kHz) and turn on the preamp. Adjust C32 and C34 for maximum signal strength. Switch to 10 meters (28200 kHz) and turn on the preamp. Adjust L12 and L13 for maximum signal strength.
If you did make a change to R1's value, you'll need to recalibrate C A L S H I and C A L S L O (owner's manual, page 84).
Switch to 12 meters (24900 kHz) and turn on the preamp. Adjust C44 and C46 for maximum signal strength.
14
Fine-Tuning Filter Settings
13. Speaker grille cloth Grille cloth (part #E850089) can optionally be added to your original K2 top cover. (The KPA100 module already has grille cloth for its speaker.)
You can optionally fine-tune your BFO settings for each mode by ear or by using a computer-based tool such as Spectrogram.
Remove the speaker from the top cover. This may involve removing the battery option (KBT2) or other top-cover options. If you do have to remove a battery, be sure to turn the battery switch OFF using the rearpanel slide switch. Also, disconnect both leads from the battery terminals and cover the terminals with tape to prevent accidental shorts.
If you have the KSB2 option (SSB adapter), and you made the recommended changes to the second crystal filter, you may wish to fine-tune the LSB and USB BFO settings so that the filters have the same noise pitch. Note: Only the SSB BFO settings for FL2, 3, and 4 should be made in receive mode. The SSB BFO settings for FL1 should be made in transmit mode, either listening to your signal locally or having a nearby station listen for you. This is because FL1 is always used in transmit mode (and for receive, when selected), whereas FL2-4 are only used in receive mode. FL2-4 can be set up differently without affecting your transmitted signal. Refer to the KSB2 manual for more details.
Trim the supplied grille cloth to the size of the speaker frame. Place the #4 fibre washers (black) at each of the top cover's four speaker mounting holes. Trim the corners of the grille cloth so it just fits between the fibre washers, not touching them. Place the speaker on top of the fibre washers and grille cloth. Secure it with four 3/8" (9.5 mm) screws, #4 lock washers, and 4-40 nuts. Do not over-tighten the nuts.
AF GAIN Potentiometer Test The following two steps apply if you made the AF GAIN potentiometer smoothness modification.
Re-install the top cover or KPA100 module.
Rotate the AF GAIN control slowly, near the counter-clockwise end of its rotation, while listening to a steady carrier (e.g., the internally-generated signal at 4.000 MHz). There should be no noticeable noise (crackles, etc.) as you rotate the control. Set the AF GAIN control to its fully counterclockwise position (minimum gain). You should hear complete silence, with no audio signal leak-through.
15
